The invention relates to the automotive industry. To be more precise, it relates to the regeneration of particle filters used in particular in diesel engine exhaust lines of vehicles of recent design.
The exhaust lines of diesel engine motor vehicles of recent design are equipped with a particle filter to reduce their emissions of solid pollutants. The walls of the particle filter collect soot which must be eliminated regularly to prevent the particle filter from becoming clogged and to return it to its nominal efficiency. Moreover, clogging of the particle filter gradually creates a back-pressure that degrades the operation of the engine. This elimination of soot, referred to as a “particle filter regeneration”, may be effected by heating the filter to a temperature higher than the combustion temperature of soot (which is normally around 550° C.) by means of the exhaust gases flowing therein. To this end, one technical solution consists in:                adding to the fuel, for example when filling the fuel tank, an additive to assist regeneration, whose function is to reduce the combustion temperature of the soot to around 450° C. and to provide available oxygen for propagation of combustion; this additive is mixed with the soot as it is formed in the combustion chamber and is contained within the bed of soot that is deposited in the filter; and        periodically carrying out post-injection or multiple injections of fuel on the inlet side of the particle filter, in particular into the cylinders of the engine during their expansion phase.        
The effect of the post-injection or multiple injections of fuel is to increase the temperature of the exhaust gases and the quantity of available hydrocarbons that they contain. These hydrocarbons are converted by an oxidation catalytic converter on the input side of the particle filter in an exothermic reaction that heats the exhaust gases to a temperature above 450° C. They then impinge on the bed of soot, where combustion of the soot occurs because of the high temperature of the exhaust gases and the catalytic activity of the additive particles and is propagated by the oxygen made available to the filter medium by the additive.
The additive for assisting regeneration is based on ceria CeO2 and/or on ferric oxide Fe2O3, for example, or on any metal oxide capable of giving up oxygen. The dose of this additive is generally from a few parts per million (ppm) to 50 ppm of the active material (cerium and/or iron).